This project identifies and characterizes biochemical mechanisms for dopamine receptors. An understanding of the biochemical phenomena contributing to the activity of dopamine receptors will identify possible mechanisms of action for drugs used to treat Parkinson's disease, endocrine disorders, and psychiatric disorders. Among the topics studied in the current fiscal year are: 1) in vitro characterization of the D-2 receptor in the intermediate lobe of the rat pituitary gland; 2) identification of the kinetic and biochemical consequences of stimulation of the D-2 receptor; and 3) identification of the role of GTP in the functioning of the D-2 receptor.